1. Field of the Invention
The present invention relates to a digital camera and imaging method that stores image information obtained by an imaging device in a recording medium and more particularly to a power-thrifty digital camera, which controls power consumption of a battery or the like.
2. Discussion of the Background
A camera using a photographic film (i.e. a silver halide film camera) has been generally used for photography. Recently, digital cameras have become increasingly widespread. In the digital cameras, an object image is photographed by a solid-state imaging device, such as a charged coupled device (CCD) or the like, and image data of the object image, such as static images (still images) and moving images (movie images), are obtained and digitally recorded in an IC (integrated circuit) card, such as a printed circuit (PC) card with semiconductor memory, a video floppy disk, or the like.
Digital cameras have many photographing modes for imaging objects by the solid-state imaging device other than a normal photographing mode in which a single static image is obtained every time a shutter releases. These modes include the following: (1) a continuous shoot mode in which multiple static images are successively obtained at a predetermined time interval when the an operator continuously depresses a shutter release device; (2) an auto bracketing mode in which a same static image is photographed with different predetermined multiple exposure values corresponding to a shutter release operation; and (3) a movie capture mode in which moving images are obtained each time the shutter releases in response to the shutter release device being continuously depressed. In the above-described digital camera, almost all functions, except for optical sub-systems are digitally performed, e.g., basic photographing functions, add-on accessory functions, etc.
In the digital camera, much electric power tends to be consumed for supporting components, which include an imaging device, a lens driving motor, an electronic flash, a display part, etc. As the digital camera is usually equipped as a portable device for photographing various events, battery power, such as a primary cell and a storage cell, is used as a main operation power. When the battery gets weak, the digital camera loses its ability to function and cannot continue to photograph without the assistance of a spare battery. For example, the digital camera may continue to operate on four AA batteries for 20 to 40 minutes, and for 1 to 2 hours on a lithium battery. However, the present invention attempts to increase operational time by reducing the consumption of electric power as much as possible in the digital camera.
Various methods have been employed to reduce the consumption of electric power. For example, in non-photographing modes, especially when photographed image data are read out, displayed and transmitted to other devices, such as a computer, the digital camera is made to use auxiliary power sources such as utility AC (alternating current) power from an electrical outlet, a car battery via an AC adapter or the like. Further, in order to reduce the consumption of electric power in the photographing mode, the power source is automatically turned off after a predetermined time has elapsed while the camera operated in a standby condition. Furthermore, indications such as displays or lights corresponding to functions that are not used in an active operational mode are selectively turned off.
Recently, the number of digital cameras having a liquid crystal display (hereinafter referred to as an LCD) has increased. In such digital cameras, the LCD is used to display photographed images and is used as an electronic viewfinder in a photographing mode. However, the LCD consumes much electric power, not only for driving a display, but also for backlighting for a translucent display. Therefore, the inventors recognize that it is preferable for saving electric power to use an optical viewfinder instead of a LCD electronic viewfinder in a photographing mode.
When an operator photographs an image with the optical viewfinder, the operator often has a demand for viewing the photographed image at that moment. As a result, the operator displays the photographed image on the LCD right after photographing and checks the image.
However, performing display operations every time an image is photographed becomes a burden on the operator. Further, there are concerns about increasing the consumption of the battery power resulting from driving the LCD for a long time.